This relates generally to computer systems and, particularly, to system management interrupt (SMI) handlers.
A system management mode is an operating mode that enables an operating system transparent interrupt, known as a system management interrupt. The system management interrupt enables basic input/output system firmware to handle various platform level events at runtime. The basic input/output system system management interrupt handler has full and unfettered access to all hardware that is visible to normal operating system software.
A trusted computing system is any information system where access to data is controlled in a manner that restricts access to the data to a known set of hardware and software components. As used in that definition, data is information, secrets, and applications. Any component that has unfettered access to the data is known as a member of the trusted computing base (TCB). A member of the trusted computer base has access to the data and, therefore, the member must be trusted to work correctly. Access to data by non-TCB components is controlled explicitly by TCB components according to the TCB security policy.
Trusted execution technology establishes a trusted computing base using a launch process that begins in microcode. See Intel® Trusted Execution Technology, Preliminary Architecture Specification, November 2006, available from Intel® Corporation, Santa Clara, Calif. Software components in use during the launch process are cryptographically measured using a cryptographic hash algorithm. The component measurement values, or identity of the component, are securely stored in a trusted platform module using the extend mechanism provided by the trusted platform module. The identity of the trusted computing base is the cumulative identities, or measured values, of all of the trusted execution components.